diff --git a/toolkit/components/places/PlacesBackups.jsm b/toolkit/components/places/PlacesBackups.jsm
index e1b0b71370b..95c910875b8 100644
--- a/toolkit/components/places/PlacesBackups.jsm
+++ b/toolkit/components/places/PlacesBackups.jsm
@@ -233,7 +233,7 @@ this.PlacesBackups = {
     let dateObj = aDateObj || new Date();
     // Use YYYY-MM-DD (ISO 8601) as it doesn't contain illegal characters
     // and makes the alphabetical order of multiple backup files more useful.
-      return "bookmarks-" + dateObj.toLocaleFormat("%Y-%m-%d") + ".json" +
+      return "bookmarks-" + dateObj.toISOString().substr(0, 10) + ".json" +
                             (aCompress ? "lz4" : "");
   },
 
diff --git a/toolkit/components/places/tests/bookmarks/test_1016953-renaming-uncompressed.js b/toolkit/components/places/tests/bookmarks/test_1016953-renaming-uncompressed.js
index 1b0d6802818..bfe7947df6d 100644
--- a/toolkit/components/places/tests/bookmarks/test_1016953-renaming-uncompressed.js
+++ b/toolkit/components/places/tests/bookmarks/test_1016953-renaming-uncompressed.js
@@ -20,7 +20,7 @@ add_task(function* test_same_date_same_hash() {
 
   // Save JSON file in backup folder with hash appended
   let dateObj = new Date();
-  let filename = "bookmarks-" + dateObj.toLocaleFormat("%Y-%m-%d") + "_" +
+  let filename = "bookmarks-" + dateObj.toISOString().substr(0, 10) + "_" +
                   count + "_" + hash + ".json";
   let backupFile = OS.Path.join(backupFolder, filename);
   yield OS.File.move(tempPath, backupFile);
@@ -53,7 +53,7 @@ add_task(function* test_same_date_diff_hash() {
                               "bug10169583_bookmarks.json");
   let {count, hash} = yield BookmarkJSONUtils.exportToFile(tempPath);
   let dateObj = new Date();
-  let filename = "bookmarks-" + dateObj.toLocaleFormat("%Y-%m-%d") + "_" +
+  let filename = "bookmarks-" + dateObj.toISOString().substr(0, 10) + "_" +
                   count + "_" + "differentHash==" + ".json";
   let backupFile = OS.Path.join(backupFolder, filename);
   yield OS.File.move(tempPath, backupFile);
@@ -84,9 +84,9 @@ add_task(function* test_diff_date_same_hash() {
   let {count, hash} = yield BookmarkJSONUtils.exportToFile(tempPath);
   let oldDate = new Date(2014, 1, 1);
   let curDate = new Date();
-  let oldFilename = "bookmarks-" + oldDate.toLocaleFormat("%Y-%m-%d") + "_" +
+  let oldFilename = "bookmarks-" + oldDate.toISOString().substr(0, 10) + "_" +
                   count + "_" + hash + ".json";
-  let newFilename = "bookmarks-" + curDate.toLocaleFormat("%Y-%m-%d") + "_" +
+  let newFilename = "bookmarks-" + curDate.toISOString().substr(0, 10) + "_" +
                   count + "_" + hash + ".json";
   let backupFile = OS.Path.join(backupFolder, oldFilename);
   let newBackupFile = OS.Path.join(backupFolder, newFilename);
diff --git a/toolkit/components/places/tests/bookmarks/test_477583_json-backup-in-future.js b/toolkit/components/places/tests/bookmarks/test_477583_json-backup-in-future.js
index 5e9b71d26d5..46b88cd3119 100644
--- a/toolkit/components/places/tests/bookmarks/test_477583_json-backup-in-future.js
+++ b/toolkit/components/places/tests/bookmarks/test_477583_json-backup-in-future.js
@@ -21,7 +21,7 @@ function run_test() {
     let dateObj = new Date();
     dateObj.setYear(dateObj.getFullYear() + 1);
     let name = PlacesBackups.getFilenameForDate(dateObj);
-    do_check_eq(name, "bookmarks-" + dateObj.toLocaleFormat("%Y-%m-%d") + ".json");
+    do_check_eq(name, "bookmarks-" + dateObj.toISOString().substr(0, 10) + ".json");
     files = bookmarksBackupDir.directoryEntries;
     while (files.hasMoreElements()) {
       let entry = files.getNext().QueryInterface(Ci.nsIFile);
diff --git a/toolkit/components/places/tests/bookmarks/test_818584-discard-duplicate-backups.js b/toolkit/components/places/tests/bookmarks/test_818584-discard-duplicate-backups.js
index 30efb0e0ebf..8e100fbcb5e 100644
--- a/toolkit/components/places/tests/bookmarks/test_818584-discard-duplicate-backups.js
+++ b/toolkit/components/places/tests/bookmarks/test_818584-discard-duplicate-backups.js
@@ -33,7 +33,7 @@ add_task(function() {
   do_check_eq(backupFiles.length, 1);
   
   let matches = OS.Path.basename(backupFiles[0]).match(PlacesBackups.filenamesRegex);
-  do_check_eq(matches[1], new Date().toLocaleFormat("%Y-%m-%d"));
+  do_check_eq(matches[1], new Date().toISOString().substr(0, 10));
   do_check_eq(matches[2], count);
   do_check_eq(matches[3], hash);
 
@@ -49,7 +49,7 @@ add_task(function() {
   recentBackup = yield PlacesBackups.getMostRecentBackup();
   do_check_neq(recentBackup, OS.Path.join(backupFolder, oldBackupName));
   matches = OS.Path.basename(recentBackup).match(PlacesBackups.filenamesRegex);
-  do_check_eq(matches[1], new Date().toLocaleFormat("%Y-%m-%d"));
+  do_check_eq(matches[1], new Date().toISOString().substr(0, 10));
   do_check_eq(matches[2], count + 1);
   do_check_neq(matches[3], hash);
 
diff --git a/toolkit/components/places/tests/head_common.js b/toolkit/components/places/tests/head_common.js
index a1b31a8fbb1..8e222775df5 100644
--- a/toolkit/components/places/tests/head_common.js
+++ b/toolkit/components/places/tests/head_common.js
@@ -402,7 +402,7 @@ function shutdownPlaces(aKeepAliveConnection)
 
 const FILENAME_BOOKMARKS_HTML = "bookmarks.html";
 const FILENAME_BOOKMARKS_JSON = "bookmarks-" +
-  (new Date().toLocaleFormat("%Y-%m-%d")) + ".json";
+  (new Date().toISOString().substr(0, 10)) + ".json";
 
 /**
  * Creates a bookmarks.html file in the profile folder from a given source file.
@@ -514,7 +514,7 @@ function check_JSON_backup(aIsAutomaticBackup) {
     let bookmarksBackupDir = gProfD.clone();
     bookmarksBackupDir.append("bookmarkbackups");
     let files = bookmarksBackupDir.directoryEntries;
-    let backup_date = new Date().toLocaleFormat("%Y-%m-%d");
+    let backup_date = new Date().toISOString().substr(0, 10);
     while (files.hasMoreElements()) {
       let entry = files.getNext().QueryInterface(Ci.nsIFile);
       if (PlacesBackups.filenamesRegex.test(entry.leafName)) {
diff --git a/toolkit/components/places/tests/unit/test_utils_backups_create.js b/toolkit/components/places/tests/unit/test_utils_backups_create.js
index 98b791cec24..ddbd948fa3e 100644
--- a/toolkit/components/places/tests/unit/test_utils_backups_create.js
+++ b/toolkit/components/places/tests/unit/test_utils_backups_create.js
@@ -23,7 +23,7 @@ add_task(function () {
     let randomDate = new Date(dateObj.getFullYear() - 1,
                               Math.floor(12 * Math.random()),
                               Math.floor(28 * Math.random()));
-    let dateString = randomDate.toLocaleFormat("%Y-%m-%d");
+    let dateString = randomDate.toISOString().substr(0, 10);
     if (dates.indexOf(dateString) == -1)
       dates.push(dateString);
   }
@@ -49,7 +49,7 @@ add_task(function () {
 
   yield PlacesBackups.create(NUMBER_OF_BACKUPS);
   // Add today's backup.
-  dates.push(dateObj.toLocaleFormat("%Y-%m-%d"));
+  dates.push(dateObj.toISOString().substr(0, 10));
 
   // Check backups.  We have 11 dates but we the max number is 10 so the
   // oldest backup should have been removed.